1. Field of the Invention
The present invention relates to a microscope adapter unit that is disposed on an optical path of illumination light.
2. Description of the Related Art
In recent years, accompanying the expansion of the scope of applications of microscopes, there has been a demand that microscopes be able to respond to various observation methods. Accordingly, microscopes that selectively realize various illumination conditions in accordance with various observation methods have been proposed.
As a method of selectively realizing illumination conditions in order to respond to observation methods, a method in which a light source unit is replaced with a different light source unit has been known conventionally. However, in recent years, a method in which an additional unit provided between the light source unit and the main body of a microscope (referred to as a microscope adapter unit hereinafter) is used without replacing light source units or in addition to the replacement of light source units is also known. A microscope utilizing a microscope adapter unit is disclosed by, for example, Japanese Laid-open Patent Publication No. 6-289301 and Japanese Laid-open Patent Publication No. 7-174975.
As a microscope adapter unit, Japanese Laid-open Patent Publication No. 6-289301 discloses a variable magnification lens unit that varies the magnification for projecting light from a light source to the pupil of an objective.
Also, Japanese Laid-open Patent Publication No. 7-174975 discloses, as a microscope adapter unit, a frame that is detachable from the body (main body of a microscope) of a microscope including a converter lens that varies the magnification of the illumination system. A dichroic mirror that switches a light source unit to another light source unit used to illuminate samples is also disclosed as a microscope adapter unit.
Demand has increased steadily over the years for optimal illumination that responds to various observation methods, and higher levels of illumination performance have also been demanded. Thus, the number of optical devices or optical units containing optical devices required to meet this demand has also increased. Accordingly, the size, especially the width in the optical axis direction (referred to as unit length, hereinafter), of a microscope adapter unit has inevitably become larger and longer so that the distance between the light source unit and the microscope main body has also inevitably become greater.
As shown in FIG. 1A, in a common microscope 100, illumination light emitted from a light source 101 is converted into roughly parallel luminous fluxes B1 by a collimation optical system 102 including a collector lens or the like, is emitted from a light source unit 103, and immediately after that, enters a microscope main body 104.
More specifically, illumination light emitted from a point on optical axis O in the light source 101 (simply referred to as on-axis illumination light, hereinafter) is converted by the collimation optical system 102 into roughly parallel luminous fluxes B1 that are parallel to optical axis O as shown in FIG. 1B. Illumination light emitted from a point not on optical axis O in the light source 101 (simply referred to as off-axis illumination light, hereinafter) are converted into roughly parallel luminous fluxes B2 that are oblique to optical axis O.